Apparatus for finishing oval workpieces



Get. 1, 1968 E. DE ALMEIDA FERREIRINHA APPARATUS FOR FINISHING OVAL WORKPIECES 4 Sheets-Sheet 1 Filed Nov. 17, 1964 cozohwao 0: 3 3 0 m1" 29.3w 0; 5 22:3 32; 0: 55 432:3 0:9. =2m2Emco: 252cm zwt w8o mg; 052:5 9: 88: v 3:30 32a 0;

33 58 9:52: uzoEogumv E. DE ALMEIDA FERREIRINHA APPARATUS FOR FINISHING OVAL WORKPIECES Filed Nov. 17, 1964 4 Sheets-Sheet 2 Oct 1, 1963 E. DE ALMEIDA FERREIRINHA 3,403,479

APPARATUS FOR FINiSHING OVAL WORKPIECES I Filed Nov. 17, 1964 4 Sheets-Sheet 5 W I 'HI 'H C .9 In 2 E m C E 0: E 8 II :02 e [up 1968 E. DE ALMEIDA FERREIRINHA APPARATUS FOR FINISHING OVAL WORKPIECES 4 Sheets-Sheet 4 Filed Nov. 17, 1964 /A mm x 8 m an United States Patent 3,403,479 APPARATUS FOR FINISHING OVAL WORKPIECES Eduardo de Almeida Ferreirinha, Rua da Boa Nova 125/163, Oporto, Portugal Filed Nov. 17, 1964, Ser. No. 411,931 Claims. (Cl. 51-105) ABSTRACT OF THE DISCLOSURE An oval workpiece is finished by rotating the workpiece about a fixed longitudinal axis, positioning cutting means in cutting relation with the peripheral surface of the workpiece and as the workpiece rotates moving the cutting means cyclically toward and away from the axis of the workpiece.

The present invention relates to a system for finishing workpieces of oval shape.

In accordance with prior practice in finishing oval workpieces, it has been necessary first to obtain a master cam having the desired size, shape and ovality. With the new system in accordance with the present invention, the need of providing a master cam is eliminated and the same results are obtained in a much simpler and more practical manner.

The system of finishing oval workpieces in accordance with the invention will be understood from the following description in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic view illustrating the system in accordance with the present invention,

FIG. 2 is an axial section of a grinding wheel for use in carrying out the invention,

FIG. 3 shows the grinding wheel of FIG. 2 partially in end elevation and partially in section taken approximately on the line 3-3 in FIG. 2,

FIG. 4 is a schematic view illustrating the manner of adjusting the eccentricity of the grinding wheel shown in FIGS. 2 and 3,

FIG. 5 is a schematic view illustrating other apparatus for carrying out the invention,

FIG. 6 is a schematic view partially in section on the line 66 in FIG. 7 illustrating in more detail, apparatus of the kind shown in FIG. 5, and

FIG. 7 is a schematic partial cross section taken approximately on the line 77 in FIG. 6.

In accordance with the present invention, the peripheral surface of a workpiece of oval cross section is finished by rotating the workpiece about a fixed longitudinal axis, positioning cutting means in cutting relation with the peripheral surface of the workpiece and moving the cutting means cyclically toward and away from the axis of the workpiece in selected time and phase relationship with the rotation of the workpiece. Each cycle of movement of the cutting means has a period equal to one half revolu tion of the workpiece. The amount of movement of the cutting means toward and away from the axis of the workpiece is equal to one half of the desired ovality of the workpiece. By ovality, is meant the different between the transverse dimensions of the workpiece measured respectively along the major and minor axes of the oval cross section.

As illustrated in the accompanying drawings, apparatus for finishing workpieces of oval cross section in accordance with the invention comprise means for rotating the workpiece about a first fixed axis, means for cutting the workpiece while it is rotated, means including an eccentric rotatable about a second fixed axis parallel to the first axis for cyclically varying the distance between an active porice tion of the cutting means and the axis of rotation of the workpiece and means for rotating the eccentric in selected time and phase relationship with the workpiece at a speed equal to twice the speed of the workpiece, the eccentricity of the eccentric being equal to one fourth of the ovality to be imparted to the workpiece. The cutting means may, for example, be a grinding wheel or a diamond or other cutting tool. In the case of a grinding wheel, the active portion is considered as being the portion which is at a given instant in engagement with the workpiece. The eccentric for varying the distance between an active portion of the cutting means and the axis of rotation of the workpiece, may, for example, comprise an eccentric mounting of a grinding wheel or an eccentric cam arrangement for moving a cutting tool toward and away from the workpiece axis.

The system for finishing a workpiece of oval cross section in accordance with the present invention by means of an eccentrically mounted grinding wheel is illustrated schematically in FIG. 1. A workpiece W which is to be finished, is mounted on a first shaft or spindle 1 rotatable about its axis A1 and a grinding wheel G is mounted on a second shaft or spindle 2 rotatable about an axis A2. The two shafts are coupled by suitable transmission means so that the grinding wheel G turns at twice the speed of the workpiece W. The grinding wheel is initially dressed to roundness, for example, by conventional dressing means and is then mounted off center of its axis of rotation as will be described more fully below to provide an eccentricity e as illustrated in FIG. 1. When the workpiece and grinding wheel are then rotated in timed relation to one another with the speed of the grinding wheel twice that of the workpiece, the grinding wheel will produce on the workpiece, a surface having an ovality equal to four times the eccentricity e of the grinding wheel. During the rotation of the workpiece and grinding wheel, the two are maintained in correct phase relation as illustrated in FIG. 1

In FIGS. 2, 3 and 4, there is illustrated by way of example a practical method of mounting the grinding wheel eccentrically. A hub 4 is provided with a tapered bore 5 and is adapted to be mounted on a rotating spindle, for example the shaft of a lathe. At one end, the hub 4 is provided with an annular flange 6 while the other end 7 is externally threaded and is counterbored to receive a nut for securing the hub on the spindle or shaft on which it is mounted. A spider 8 surrounding the hub and secured to it by a key 9 has opposite radially projecting arms 11, the outer end portions of which are received between lugs 12 on the inner periphery of a support ring 13 of an annular grinding wheel 14. The engagement of the arms 11 between the lugs 12 provides a driving connection caus ing the support ring 13 and grinding wheel 14 to rotate with the hub 4 while permitting a certain amount of movement between the hub and grinding wheel in a radial direction for the purpose of adjusting the eccentricity of the grinding wheel with respect to the hub as will be described below.

Two axially spaced inner rings 16 and 17 are rotatably mounted on the hub 4 on opposite sides of the spider 8 and have conical outer peripheries which are eccentric with respect to the hub as illustrated schematically in FIG. 4. Rotatable on the outer peripheries of the inner rings 16 and 17, there are two outer rings 18 and 19 which have conical inner peripheries matching the conical outer peripheries of the inner rings 16 and 17 and outer peripheries having spherical surfaces matching corresponding spherical surfaces provided on the inner periphery of the grinding wheel support ring 13. The inner peripheries of the outer rings 18 and 19 are eccentric with respect to the outer peripheries by an amount equal to the eccentricity of the inner rings 16 and 17 as illustrated in FIG. 4. The entire assembly comprising the spider 8 support ring 13, grinding wheel 14 and inner and outer rings 16-19 is secured on the hub 4 by means of a nut 21 screwed onto the threaded end 7 of the hub and pressing resiliently on the inner ring 16 through spring washers 22. The inner and outer rings 1619 and grinding wheel support ring 13 are held in assembled relation with one another between the spring washer 22 and the flange 6 of the hub by reason of their conical and spherical interengaging surfaces as described above. Since the parts are held in place resiliently rather than rigidly, it is possible to turn the inner and outer rings relative to one another to adjust the eccentricity of the grinding wheel as will now be described.

The inner and outer rings 16, 18 can be turned relative to one another by means of a shaft 25 which is rotatably supported in the spider 8 and is provided with pinions 26 and 27 engaging respectively gear teeth provided on the inner and outer rings. Inner and outer rings 17 and 19 can similarly be turned relative to one another by means of a shaft 28 rotatably mounted in the spider 8 and provided with pinions 29 and 30 engaging respectively gear teeth provided on the inner and outer rings. The two sets of inner and outer rings can thus be adjusted independently of one another.

When the eccentricities of the inner and outer rings are opposite one another as illustrated in FIG. 4, the grinding wheel is centered with respect to the axis A2. With the rings in this position, the grinding wheel is dressed so as to be concentric with the axis of rotation. If the inner and outer rings are now turned relative to one another in the directions indicated respectively by the arrows F1 and F2 in FIG. 4, the grinding wheel is moved off center of the axis in the direction indicated by the arrow F3 by an amount proportional to the amount the inner and outer rings are turned relative to one another. As will be understood from the foregoing description, the two pairs of rings 16, 18 and 17, 19 can be shifted independently of one another. This results in the possibility of positioning the grinding wheel so that the eccentricity at one end face is different from that at the other end face. In this manner, it is possible to obtain finished parts having greater ovality at one end than at the other provided the length of the parts does not exceed that of the grinding wheel.

Suitable indicia or graduations may be provided on adjacent portions of the inner and outer rings 16, 18 and 17, 19 in order to indicate with precision, the eccentricity and any angular deviation of the grinding wheel with respect to the axis of rotation. It will be understood that the grinding wheel is used in the manner illustrated in FIG. 1 to finish a workpiece of oval cross section.

FIGS. 5, 6 and 7 illustrate the finishing of workpieces of oval cross section by means of a cutting tool, for example a tool like those used in a lathe. A workpiece W, which is shown as a piston for an engine, is mounted concentrically on a work spindle 31 which is connected with the drive shaft 32 of an oval generating unit 33 by means of a transmission 34 and a telescopic connection 35 having universal joints 36. The transmission 34, which, may for example, be a chain drive, provides a speed ratio of 2 to 1 between the drive shaft 32 of the oval generating unit 33 and the work spindle 31.

As shown in FIGS. 6 and 7, the oval generating unit 33 comprises a housing 37 in which the shaft 32 is rotatably mounted by means of bearings 38. An elongated bushing 40 is splined on the shaft 32 so as to rotate therewith, but is slidable lengthwise of the shaft. The bushing 40 is of generally cylindrical shape, but is inclined with respect to the axis of the shaft 32 so that a left end portion as viewed in FIG. 6 is concentric with the shaft while a right hand portion is eccentric with respect to the shaft. A ring 41 is splined on the bushing 40 so as to rotate therewith, but be slidable lengthwise of the bushing. The inner bore of the ring 41 which engages the bushing 40 is inclined with respect to the cylindrical outer periphery of the ring so that the axis of the outer periphery is parallel to that of the shaft 32. The outer periphery of the ring 41 is engaged by a connecting rod 42 which is connected by a wrist pin 43 with a cutting tool holder 44 in which a suitable cutting tool 45 is secured, for example by set screws 46. A tail 47 on the connecting rod is received between guides 48 (FIG. 7) on the housing to assist in keeping the connecting rod in proper alignment.

Means is provided for moving the bushing 40 in a lengthwise direction relative to the ring 41 and thereby shift the ring from a position concentric with the shaft 32 to a position eccentric of the shaft. In FIGS. 6 and 7, the means for shifting the bushing is illustrated as comprising a shaft 50 which is parallel to the drive shaft 32 and carries two arms 51 having portions encircling that shaft 32 and supporting thrust bearings 52 at opposite ends of the bushing 40. The shaft 50 is supported in the housing 37 by bearings 53 which permit the shaft 50 to be moved in a lengthwise direction so as to shift the bushing 40 axially of the drive shaft 32. Means for shifting the shaft 50 is illustrated as comprising a bell crank lever 54 pivotally supported at 55 on a bracket 56 extending from the housing. At one end, the lever 54 is slotted to engage a transverse pin 57 on a projecting outer end portion of the shaft 50. At the other end, the lever 54 is provided with a roller 58 engaging an inclined surface 59. Suitable means such as a tension spring is provided for biasing the roller 58 into engagement with the inclined surface 59.

As seen in FIG. 5, the oval generating unit 33 is positioned so that the cutting tool 45 is in engagement with the workpiece W. The work spindle 31 and drive shaft 32 of the oval generating unit 33 are driven in timed relation with one another through suitable power means (not shown), the shaft 32 being driven at twice the speed of the Work spindle 31. When the bushing 40 is in the right hand position shown in FIG. 6, the ring 41 is centered with respect to the shaft 32 and hence no reciprocating movement is imparted to the cutting tool 45. The workpiece W will hence be machined circular. If the bushing 40 is shifted toward the left, the ring 41 is displaced so as to be eccentric to the shaft 32 and will hence impart to the cutting tool 45 a cyclical reciprocatory movement toward and away from the axis of the work spindle 31. This will produce an oval surface on the workpiece. The amount of eccentricity of the ring 41 and hence the amount of ovality of the workpiece, will depend on the amount the bushing 40 is shifted toward the left. The ovality of the workpiece will be equal to four times the eccentricity of the ring 41.

If it is desired to machine a workpiece having an ovality which progressively increases from one end toward the other, the oval generating unit 33 is mounted on a suitable carriage, for example, the carriage of a lathe movable parallel to the work spindle 31, while the inclined surface 59 is mounted stationary on the bed of the machine. Hence, as the oval generating unit 33 is moved lengthwise of the workpiece as indicated by the arrows in FIG. 5, the roller 58 correspondingly moves along the inclined plane 59 so as to shift the bushing 40 progressively lengthwise of the shaft 32, thereby progressively changing the eccentricity of the ring 41 and hence the ovality of the workpiece. The rate of change of eccentricity may be varied by varying the angle of inclination of the inclined surface 59.

While preferred embodiments of apparatus for canrying out the present invention have been shown by Way of example in the drawings, it will be understood that the novel system of finishing workpieces of oval cross section is in no way limited to the embodiments illustrated in the drawings and specifically described.

What I claim is:

1. Apparatus for finishing workpieces of oval cross section which comprises means for rotating said workpiece about a first fixed axis, means for cutting said workpiece while rotated, :means including an eccentric rotatable about a second fixed axis parallel to said first axis for cyclically varying the distance between an active portion of said cutting means and said first axis, means for rotating said eccentric in timed relation with said workpiece and at twice the speed of said workpiece, the eccentricity of said eccentric being equal to one fourth of the ovality to be imparted to the workpiece, said cutting means comprising a circular annular grinding wheel and said eccentric comprising means for mounting said grinding wheel eccentrically on said second axis.

2. Apparatus according to claim 1, in which said mounting means comprises a central hub, a first annular member having a circular inner periphery concentrically engaging said hub and a circular outer periphery eccentric with respect to said inner periphery, a second annular member having a circular inner periphery engaging the outer periphery of said first annular member and an outer circular periphery eccentric with respect to its inner periphery and engaging the inner periphery of said annular grinding wheel, the eccentricity of said second annular member being equal to the eccentricity of said first annular member, and means for rotating said annular members relative to one another and retaining them in selected portions, whereby the eccentricity of said grinding wheel relative to said hub can be selected.

3. Apparatus according to claim 1, in which said mounting means comprises means for tilting the axis of said annular grinding wheel relative to said shaft.

4. Apparatus according to claim 3, in which said mounting means comprises a central hub having an axial extent, axially spaced first and second inner annular members each having a circular inner periphery concentrically engaging said hub and a circular outer periphery eccentric with respect to said inner periphery, first and second oute-r annular members having circular inner peripheries engaging respectively the outer peripheries of said inner annular members and circular outer peripheries eccentric with respect to their inner peripheries and engaging axially spaced portions of the inner periphery of said annular grinding wheel, the eccentricity of said outer annular members being equal to the eccentricity of said inner annular members respectively, means for rotating said first inner and outer annular members relative to one another and retaining them in selected position and rneans for rotating said second inner and outer annular members relative to one another and retaining them in selected position.

5. Apparatus according to claim 4, in which the outer peripheries of said outer annular members and engaging surfaces of said grinding wheel are part-spherical.

References Cited UNITED STATES PATENTS 167,614 9/1875 Koch et a1. 1421O 721,516 2/ 1903 Hanson 51-101 2,290,341 7/1942 Levit 8218 2,597,167 5/1952 Musyl 51-90 X 2,685,154 8/1954 Ballinger 5190 2,909,010 10/ 1959 Von Zelewsky 5 1-90 LESTER M. SWINGLE, Primary Examiner. 

